Fair hierarchical secret sharing scheme based on smart contract

Abstract

Secret sharing has a number of practical applications in network-based scenarios, such as key transfer protocols, attribute-based encryption and secure multiparty computation. However, existing secret sharing schemes cannot efficiently achieve fairness. They either rely on a trusted third party or require multiple rounds of communication. In this paper, we propose the first decentralized and fair hierarchical threshold secret sharing (HTSS) scheme using blockchain. In the scheme, secret shares are distributed to different levels of parties, and any authorized subset of parties can obtain the secret. We leverage a smart contract to force all participants to commit to the secret shares; otherwise, the committer either reveals his secret share within a certain time frame or pays a fine. Thus, unlike previous HTSS schemes, the participants can reconstruct the secret fairly using Birkhoff interpolation without a trusted party and complete the computation in one round. We formally prove that our scheme is secure. We evaluate the performance of the scheme by implementing our scheme on Ethereum’s official test network. Our experiments show that our scheme can run reasonably fast and is practical.